This invention relates, in general, to the treatment of production intervals traversed by a wellbore to stimulate hydrocarbon production and prevent the production of fine particulate materials and, in particular, to a single trip method for selectively fracture packing multiple formations traversed by the wellbore.
It is well known in the subterranean well drilling and completion art that hydraulic fracturing of a hydrocarbon formation is sometimes necessary to increase the permeability of the production interval adjacent the wellbore. According to conventional practice, a fracture fluid such as water, oil, oil/water emulsion, gelled water, gelled oil, CO2 and nitrogen foams or water/alcohol mixture is pumped down the work string with sufficient volume and pressure to open multiple fractures in the production interval. The fracture fluid may carry a suitable propping agent, such as sand, gravel or engineered proppants, into the fractures for the purpose of holding the fractures open following the fracturing operation.
During the fracture operation, the fracture fluid must be forced into the formation at a flow rate great enough to generate the required pressure to fracture the formation allowing the entrained proppant to enter the fractures and prop the formation structures apart. The proppants produce channels which will create highly conductive paths reaching out into the production interval, which increases the reservoir permeability in the fracture region. As such, the success of the fracture operation is dependent upon the ability to inject large volumes of hydraulic fracture fluid along the entire length of the formation at a high pressure and at a high flow rate.
It has been found, however, that it is difficult to achieve the desired stimulation of multiple zones traversed by a single wellbore. Specifically, when multiple production intervals are fractured at the same time, one of the zones will typically dominate and take a vast majority of the treatment fluids. While this dominant zone may be properly stimulated, the other less dominant zones may receive little or no treatment fluids resulting in little or no stimulation.
Therefore a need has arisen for a method of selectively frac packing multiple zones traversed by a wellbore such that tailored fracture treatments may be preformed on each of the zones. A need has also arisen for such a method that is capable of creating fractures along the entire length of each of the zones. Further a need has arisen for such a method that is capable of stimulating each of the zones to enhance production and capable of packing each of the production intervals to prevent the production of fine particulate materials when production commences.
The present invention disclosed herein comprises a single trip method of selectively frac packing multiple zones traversed by a wellbore such that tailored fracture treatments may be preformed on each of the zones. The method of the present invention is capable of creating fractures along the entire length of each of the zones. Further, the method of the present invention is capable of stimulating each of the zones to enhance production and is also capable of packing each of the production intervals to prevent the production of fine particulate materials when production commences.
In the single trip method of the present invention, a first screen assembly having a plurality of first valves is located within the wellbore proximate a first formation and a second screen assembly having a plurality of second valves is located within the wellbore proximate a second formation. A service tool is then run downhole and positioned proximate the first formation such that a first fracture treatment fluid may be pumped through the service tool into of the first screen assembly. The first valves are then progressively operated to establish fluid communication from the interior to the exterior of the first screen assembly such that the first formation is progressively fractured. The service tool is then repositioned proximate the second formation such that a second fracture treatment fluid may be pumped into the interior of the second screen assembly. Thereafter, the second valves are progressively operated to establish fluid communication from the interior to the exterior of the second screen assembly such that the second formation is progressively fractured.
The present invention allows for a tailored treatment regimen to be delivered to each formation. As an example, the first and second fracture treatment fluids may have substantially the same composition or may have different compositions. Likewise, the first and second fracture treatment fluids may have substantially the same viscosity or may have different viscosities. In addition, the first and second fracture treatment fluids may be injected at substantially the rate or may be injected at different rates.
The first and second fracture treatment fluids may include solid agents therein. The solid agents not only prop the fractures in the first and second formations to create a highly permeable path to the wellbore, but also, pack the wellbore adjacent to the first and second formations to prevent the production of fines therethrough.
During and following the treatment process, the flow of fluids from the exterior to the interior of the first and second screen assemblies through the first and second valves is prevented as the first and second valves are preferably one-way valves only allowing fluid flow from the interior to the exterior of the first and second screen assemblies. In addition, during the treatment process, the flow of fluids between the interior and the exterior of the first and second screen assemblies through the openings in the base pipes of the first and second screen assemblies is prevented with seal members. Following the treatment process, however, the seal members must be removed. Depending upon the type of seal members used, the removal process may involve combustion, vibration, chemical reaction, mechanical removal or the like.
The progressive operation of the first valves may progress from the far end, the end having a greater hole depth, to the near end, the end having a lesser hole depth, of the first screen assembly. Alternatively, the progressive operation of the first valves may progress from the near end to the far end of the first screen assembly. Likewise, the progressive operation of the second valves may progress from the far end to the near end or the near end to the far end of the second screen assembly.
The first and second valves may be progressively operated in response to pressure within their respective screen assemblies. Alternatively, the progressive operation of the first and second valves may be achieved via wireless telemetry, a direct electrical connection, a hydraulic connection or the like.